Degradation that occurs when wave division multiplexed (WDM) and dense wave division multiplexed (DWDM) optical signals are transmitted over a length of optical fiber is a primary concern in optical networking. There are many known factors that contribute to this degradation, and controlling each of those factors is necessary to successfully transmit a plurality of optical channels through an optical fiber. In particular, optical waveforms carried on optical channels are distorted by a plurality of non-linear optical transmission effects, including phenomena known as 4-wave mixing, and soliton WDM jitter, which are especially pronounced when the bit rate of the optical signal approaches or exceeds 20 Gb/s.
Methods and apparatus for reducing signal degradation due to non-linear optical transmission effects are taught in various patents, such as U.S. Pat. No. 6,181,858 entitled DISPERSION SHIFTED FIBER that issued to Kato et al. on Jan. 30, 2001, and U.S. Pat. No. 6,181,449 entitled WAVELENGTH DIVISION MULTIPLEXED OPTICAL PROCESSING DEVICE AND OPTICAL COMMUNICATIONS TRANSMISSION PATH that issued to Taga et al. on Jan. 30, 2001. These patents, as well as others, teach improvements to transmission using various physical layer devices and media. For example, controlled and select doping of optical fibers is taught in numerous United States patents, such as U.S. Pat. No. 6,181,858, to reduce 4-wave mixing. The use of waveguide correction devices taught in U.S. Pat. No. 6,181,449, limits non-linear optical transmission effects, such as those caused by soliton effects. However, these inventions concentrate on the physical layer of the optical network.
Other cost efficient methods for reducing the degradation of optical waveforms caused by four-wave mixing and soliton WDM jitter, remain highly desirable.